JP2001259665A - Hydrosulfite production waste liquid treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively and economically treating the waste liquid generating from a hydrosulfite producing equipment without using any large-scale apparatus and much energy. SOLUTION: Sodium formate is recovered by separating a hydrosulfite product from a reaction solution and by subjecting the production waste liquid from which alcohol is distilled off and recovered to electrodialysis and residual waste liquid is subjected to activated sludge treatment after subjecting the residual waste liquid to oxidation-treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste liquid generated from a reaction step in the production of hydrosulfite by a sodium formate method.

[0002]

2. Description of the Related Art When industrially producing hydrosulfite, a sodium formate method in which sodium formate, sulfurous anhydride and an alkali agent are reacted in a hydrous alcohol (JCIA, December, 1969, 713-719). See page)
Is widely used. In the sodium formate method, unreacted sodium formate, by-product formate, sodium acid sulfite, sodium thiosulfate, alcohol, and the like are present in the filtrate obtained by separating the hydrosulfite product from the reaction solution. Conventionally, the alcohol in the filtrate is recovered by distillation as a reaction solvent, and the aqueous solution after the alcohol is distilled off is treated as a waste liquid.

[0003] Wastewater from a chemical factory or the like is regulated by the Water Pollution Prevention Law to contain organic substances or the like at a predetermined concentration or less. The management criteria for organic substances are indicated by BOD (biochemical oxygen demand), etc.
It can be managed by OD (total oxygen consumption). Since a large amount of sodium formate, sodium acid sulfite, and sodium thiosulfate is present in the hydrosulfite production waste liquid, it becomes a high TOD source in the wastewater and cannot be discharged out of the factory as it is. Therefore, it is discharged after the TOD is reduced by activated sludge treatment or the like.

[0004]

In order to reduce a large amount of wastewater having a high concentration TOD to a reference value or less by activated sludge treatment, a vast site and equipment are required. Further, sodium sulfates in the waste liquid can be decomposed by mild wet oxidation, but sodium formate cannot be decomposed, and a sufficient reduction in TOD cannot be expected. Further, as a method for completely decomposing sodium formate in the waste liquid to reduce TOD, there is a high-temperature wet oxidation method using a Ru catalyst, but this method is not economical because it requires a large amount of energy. An object of the present invention is to provide a method for effectively and economically treating a waste liquid generated from a hydrosulfite production facility without using a large-scale facility or a large amount of energy.

[0005]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, sodium salt comprising monovalent anions such as sodium formate was subjected to electrodialysis from a hydrosulfite production waste liquid. After recovering (1 sodium salt) and reducing the TOD in the waste liquid, the remaining waste liquid containing a sodium salt (disodium salt) composed of a divalent anion such as sodium thiosulfate is subjected to oxidation treatment, and then the activity is reduced. The present inventors have found that effective treatment of waste liquid can be achieved by sludge treatment, and arrived at the present invention. That is, the present invention provides a method for producing hydrosulfite by a sodium formate method, wherein sodium formate is recovered by electrodialysis with respect to a production waste liquid obtained by distilling and recovering alcohol from a filtrate obtained by separating a hydrosulfite product from a reaction solution. A method for treating a hydrosulfite production waste liquid, comprising oxidizing the remaining waste liquid and then subjecting it to activated sludge treatment.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the electrodialysis apparatus used in the present invention can be a known structure without any particular limitation. An electrodialysis apparatus is constituted by alternately arranging a cation exchange membrane and a monovalent anion selective permeable membrane between electrodes to form a desalting chamber, a concentration chamber, and an electrode chamber in contact with both electrodes. .
The most preferable structure is a so-called filter press type structure in which cation exchange membranes and anion exchange membranes are alternately arranged via a frame chamber having a cutout to form each chamber, and tightened from both ends. Each chamber frame is provided with a liquid supply port and a liquid discharge port, and each liquid supply port and discharge port is connected to a main pipe via a branch pipe as necessary. In addition, it is general to provide a spacer having a flow distribution function for making the thickness of the chamber frame uniform within the chamber frame.

As the electrode for electrodialysis in the present invention, known electrodes can be used without any limitation. That is, platinum, titanium / platinum, carbon, nickel, ruthenium / titanium, iridium / titanium and the like are often used as the anode. As the cathode, iron, nickel, platinum, titanium / platinum, carbon, stainless steel and the like are often used. As a general structure, nove board shape, mesh shape,
Lattice shape and the like.

In the present invention, the cation exchange membrane used is not particularly limited, and for example, a strongly acidic styrene-divinylbenzene-based uniform cation exchange membrane can be used. As the anion-exchange membrane, a monobasic anion-exchange membrane of a general strong basic styrene-divinylbenzene type cannot effectively separate monovalent and divalent anions. Used.

FIG. 1 is a schematic structural view showing one example of an electrodialysis apparatus used in the present invention. Two types of membranes, a cation exchange membrane (K) and a monovalent anion selective permeable membrane (A), are alternately arranged, and the desalted solution is in the desalting chamber (D) and the recovered solution is in the concentration chamber (C). be introduced. Both ends in contact with the electrodes are electrode chambers (P)
The polar solution is introduced as The number of repetitions of the arrangement of the cation exchange membrane (K) and the monovalent anion selective permeable membrane (A) can be selected according to the purpose.
1000.

In the present invention, the liquid supply to each chamber of the electrodialyzer may be performed continuously or intermittently. Further, an external tank for the supply liquid may be provided to circulate the liquid between each chamber and the external tank.

The desalting chamber is supplied with an aqueous solution (manufacturing waste liquid) obtained by distilling and recovering alcohol from the reaction filtrate obtained by separating the product from the hydrosulfite reaction solution. As electrodialysis continues, the concentration of monosodium salt such as sodium formate decreases in the desalting chamber. The liquid in which the monosodium salt has been sufficiently reduced can be appropriately withdrawn as a processing liquid and replenished with the manufacturing waste liquid. Alternatively, a continuous operation may be performed in which the processing liquid is continuously withdrawn and the manufacturing waste liquid is replenished.

[0012] 0.1-5% at the start of electrodialysis
Supply the aqueous sodium formate solution. If the electrodialysis is continued, the concentration of monosodium salt in the aqueous solution in the concentration chamber increases due to the collected sodium formate and the like. Therefore, the aqueous solution is collected as needed, and a low-concentration aqueous solution of sodium formate or water is supplied. The recovered aqueous solution contains sodium formate and sodium acid sulfite. By purifying this aqueous solution, sodium formate effective as a raw material of hydrosulfite can be recovered and reused.

An aqueous electrolyte solution of about 0.1 to 5% is supplied to the anolyte chamber. Although there is no particular limitation on the water-soluble electrolyte, sodium sulfate is particularly preferably applied in consideration of waste liquid treatment in a subsequent step.

In the present invention, the operation is performed at a current density equal to or lower than the critical current density after measuring the critical current density in advance during electrodialysis. The temperature of various liquids during electrodialysis is
Usually, it is in the range of 5 to 70C, preferably 20 to 50C.

In the present invention, when oxidizing the production waste liquid after the electrodialysis treatment, contact with air using ferric chloride as a catalyst or oxidation with aqueous hydrogen peroxide is preferred. Further, the aqueous solution recovered in the concentration chamber by electrodialysis may be purified, and the waste liquid containing sodium acid sulfite generated from the step of separating and recovering sodium formate may be oxidized together.

[0016]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples. In this example, TOD was measured by a TOD meter WQA-800 manufactured by Toray Engineering Co., Ltd.
Was used.

Example 1 In the production of hydrosulfite by the sodium formate method, a production waste liquid obtained by distilling off alcohol from a filtrate obtained by separating a hydrosulfite product from a reaction solution was subjected to an electrodialysis apparatus having a structure shown in FIG. Was used for electrodialysis. The composition of the manufacturing waste liquid was an aqueous solution of sodium thiosulfate 5.0%, sodium acid sulfite 14.0%, sodium sulfate 0.9%, and sodium formate 12.2%. Further, the TOD of the production waste liquid was 49,000 ppm. Set a strongly acidic styrene-divinylbenzene-based uniform cation exchange membrane (Serumion CMV manufactured by Asahi Glass Co., Ltd.) as a cation exchange membrane, and a monovalent anion selective permeable membrane (Seremion ASV manufactured by Asahi Glass Co., Ltd.) as an anion exchange membrane in a dialysis machine. did. The production waste liquid was supplied to a desalting chamber, and a 1% aqueous solution of sodium formate was supplied to a concentration chamber. A 3% aqueous sodium sulfate solution was supplied to the electrode chamber, and electrodialysis treatment (first time) was performed at an applied voltage of 10 V for 2 hours. An aqueous solution of 1.3% sodium formate, 2.8% sodium acid sulfite, 0.8% sodium sulfate, and 3.9% sodium thiosulfate was collected in the desalting chamber. After dialysis, the TOD of the recovered solution in the desalting chamber was measured, and was 24,000 ppm. Further, the recovered solution in the desalting chamber was subjected to ferric chloride hexahydrate 500 ppm at 40 ° C.
Was added and oxidation treatment was performed for 8 hours while blowing air. When the TOD of the liquid after the oxidation treatment was measured, it was 300 p.
pm. The temperature of the liquid is controlled at 25 ° C to 35 ° C,
When activated sludge treatment was performed under the condition of staying for 56 hours, the TOD of the treatment liquid was 1 ppm or less.

Example 2 In Example 1, when the recovered liquid in the desalting chamber was oxidized,
At 0 ° C., oxidation was performed by dropping 31% aqueous hydrogen peroxide equivalent to 1.1%. The TOD of the liquid after the oxidation treatment was measured and found to be 100 ppm. When this solution was subjected to activated sludge treatment under the same conditions as in Example 1, the TOD of the treated solution was 1 ppm.
It was below.

Comparative Example 1 The waste liquid produced in Example 1 was added with 500 ppm of ferric chloride hexahydrate at 40 ° C., and oxidized for 8 hours while blowing air. The liquid composition after the oxidation treatment is 0.4% of sodium thiosulfate, 0.5% of sodium acid sulfite, 14.6% of sodium sulfate, and 12.1% of sodium formate.
OD was 21,000 ppm. When the oxidized solution was treated with activated sludge under the same conditions as in Example 1, the TOD of the treated solution was 37 ppm.

[0020]

According to the present invention, sodium formate is recovered from hydrosulfite production wastewater by electrodialysis, and the remaining wastewater is oxidized and then treated with activated sludge, so that large-scale processing equipment and a large amount of Effective and economical waste liquid treatment that does not require energy can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing an example of an electrodialysis apparatus used in the present invention.

[Explanation of symbols]

 K cation exchange membrane A monovalent anion selective permeable membrane D desalination room C concentration room P electrode room

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 9/00 501 C02F 9/00 502R 502 502L 1/46 103 F-term (Reference) 4D006 GA17 HA47 JA42C KA03 KD30 KE16Q KE16R KE17Q KE17R MA03 MA13 MA14 PA04 PB08 PB12 PB20 PB70 4D028 AB00 BA00 4D050 AA13 AB18 BB01 BB09 BC04 4D061 DA08 DB18 DC19 EA09 EB04 EB13 EB28 EB29 EB30 EB31 EB35 ED12

Claims (3)

[Claims] In a method for producing hydrosulfite by a sodium formate method, sodium formate is recovered by electrodialysis from a production waste liquid obtained by distilling and recovering alcohol from a filtrate obtained by separating a hydrosulfite product from a reaction solution. A method for treating a hydrosulfite production waste liquid, comprising oxidizing the remaining waste liquid and then treating it with activated sludge. 2. The method for treating a hydrosulfite production waste liquid according to claim 1, wherein, during the oxidation treatment, ferric chloride is used as a catalyst and brought into contact with air. 3. The method for treating wastewater for producing hydrosulfite according to claim 1, wherein a hydrogen peroxide solution is used in the oxidation treatment.